1. Field of the Invention
This technology relates to hydraulic fracturing in oil and gas wells. In particular, this technology relates to pumping fracturing fluid into an oil or gas well using pumps powered by electric motors.
2. Brief Description of Related Art
Typically, motors are used at a well site to drive equipment. For example, diesel, gas, or electric motors might be used to drive pumps, blenders, or hydration units for carrying out hydraulic fracturing operations. Such motors are attached to the well site equipment by connecting the shaft of the motor to a shaft on the equipment, such a pump shaft for a pump, or a hydraulic motor shaft for a blender or a hydration unit. In order to compensate for misalignment between the motor and the equipment driven by the motor, a U-joint shaft is typically used. The U-joint shaft allows limited radial, angular, or even axial misalignment between the motor and the equipment, while still allowing mechanical communication between the shafts of the motor and the equipment to drive the equipment.
Use of U-joint shafts, however, can be problematic in practice. For example, U-joint shafts introduce inefficiencies into the system, losing up to 10% or more of the energy that would otherwise be transmitted from the motor shaft to the equipment. Furthermore, a minimum of 3 degrees of offset can be required between the motor and the equipment in order for the U-joint shaft to function properly. This offset leads to the need for a longer shaft, which in turn leads to greater separation between the motor and the equipment. Such separation can be problematic in setup where space is limited, for example, where both the motor and a pump are mounted to a trailer or truck body.